A comparative study of conventional drilling and helical milling of carbon-Kevlar hybrid thermoplastic composite

Combined stiffness, toughness, and recyclability of carbon–Kevlar interyarn hybrid thermoplastic composites make them suitable for increasingly used in lightweight structural applications. However, because of differences in the removal mechanisms of carbon and Kevlar fibers, coupled with matrix softening, the hole making in such type of hybrid laminate is a challenge, because it often results in machining-induced damage under conventional drilling. Helical milling is found to be a promising alternative technique to improve the hole quality and reduce thrust force, though its effectiveness for carbon–Kevlar fiber-reinforced polypropylene composites has not been properly studied yet. The present study shows a comparative experimental study between conventional drilling and helical milling. The quality of hole was evaluated on outcomes such as force, temperature, delamination, and surface integrity. Helical milling exhibited a 90.94% higher average temperature than conventional drilling, while significantly reducing thrust force (31.98%), delamination factor (33.69%), and surface roughness (39.95%). Ultimately, helical milling shows better performance in minimizing damage induced by machining and enhancing quality of hole for the considered composite.